The world's tallest luxury building can't get its superrich buyers to pay full price

Bloomberg's Oshrat Carmiel reported on Tuesday that 432 Park Ave., the slim skyscraper that's the tallest residential building in the world, has sold units this year for an average of 10% less than the original listing price.

There are too many luxury buildings in New York, and more are being constructed, which has meant high-end buyers and renters have more options and bargaining power. Meanwhile, owners have to offer more concessions to fend off their competition.

"New York City's rental market has been mostly steady, except at the high end, where the inventory has risen and rents have drifted down," the Federal Reserve said in its most recent Beige Book, based on comments from its contacts in New York.

The Fed added that landlord concessions, from price cuts to free rent, were "increasingly prevalent" in Manhattan and Brooklyn.

Jonathan Miller, president of the appraiser Miller Samuel, told Bloomberg that the 432 Park Ave. developer is likely covering for buyers' taxes because sales prices usually end in odd, unrounded numbers, suggesting subtractions were made.